Traditional telescopic, crank-up, or lattice towers, as they may be referred to in the industry, consist of several tower sections, varying in size in order to slide in and out of one another and achieve the maximum elevation. These sections are connected together through a series of cables, pulleys and a winch responsible for raising and lowering sections individually or simultaneously. The process that combines cables, pulleys and a winch is referred to as “rigging” in the industry.
A shared problem in the telescopic, crank-up, and lattice tower industry arises from the spacing between the varying sized sections. This spacing or gap is typically measured as the distance between one leg of a section and the leg of the adjacent section. Known in the industry as “play between sections,” the gap can be as small as ⅛ inch or as much as ¼ inch. While “section play” is required to allow the sections to raise and lower, it allows lateral and/or angular motion that applies undesired torque and adversely affects the overall strength and stability of telescopic, crank-up, or lattice towers with two or more sections. The effect is amplified with every additional section. In windy conditions, the play between sections creates pressure points at several different locations along the tower legs, potentially weakening these areas and increasing the probability of failure.
Some companies in the industry try to eliminate the play between sections by adding wheels, or rollers to the top of the outer section's legs, top and bottom of every inner section's legs in between and finally the lower legs of the inner most section. Unfortunately, this creates major stress on the points of contact where the wheels or rollers are located. In addition, it reduces the lifespan of the legs, pulleys and even the tower legs by creating wear points on the leg surfaces.
An improvement on this general concept involves the use of a slide bar mechanism. At the point where the slide bars meet play between sections is eliminated by the slide bars pressing up against one another. An example of this mechanism can be seen in U.S. Pat. No. 8,046,970, the contents of which are incorporated by reference herein, in their entirety. Nonetheless, further improvements are possible.